The invention relates to an exhaust gas recycle system for an internal combustion engine with an auxiliary power source for changing the position of a bypass closure valve.
A bypass control system has been made known by U.S. Pat. No. 3,842,814 in which the auxiliary valve-setting force is the vacuum in the induction tube of an internal combustion engine. The vacuum is used for varying the opening of the bypass valve by controlling the inlet opening for atmospheric air pressure in accordance with the position of the throttle valve. This system has the disadvantage that the position of the exhaust gas recycle valve cannot be made to exactly correspond to the position of the throttle valve. Furthermore, this system is very expensive and has the further disadvantage that, except when the control opening is entirely closed, the engine constantly receives bypass air in varying quantities.
Another known system proposes a cam for changing the closing member of an exhaust gas recycle valve which is coupled directly to the throttle valve shaft. While, in this system, the actuating cam can be embodied so as to move the exhaust gas recycle valve at the same time as the throttle valve, there is the distinct disadvantage that, if the exhaust gas recycle valve were to jam or if substantial friction were to develop in the linkage to the throttle valve, the latter would fail to close completely since, in general, its closure is assured only by the force of a return spring. Under such circumstances, the engine would be supplied with an excessive amount of mixture and if the engine were relieved of its load, for example by actuation of the clutch, the engine could experience an excessive speed causing destruction or damage.